This invention relates to Electric Storage Batteries. It has particular but not sole application to Automotive Starting, Lighting & Ignition Batteries, hereinafter referred to as SLI Batteries.
The conventional automotive SLI battery consists generally of six 2.2 volt Lead Acid cells connected in series. It is a primary function of the automotive battery to provide sufficient high electric current at short intervals to crank the internal combustion engine in order that it may start. The battery must also provide current to the coil in order to supply ignition at the spark plugs.
Another important function which must also be provided is that of reserve current to provide lighting and ignition for the vehicle if the vehicle's generator is not working.
The current requirements of the starter motor are vastly different from those of the vehicle's auxiliaries, such as ignition and lighting. On the one hand, cranking requires large amounts of current for a relatively short duration as the starter motor cranks the internal combustion engine against the compression of the cylinders. Ignition and other vehicle auxiliaries, however, require lower current rates but for longer periods of time.
The conventional SLI battery system is therefore designed first to provide sufficient cranking power, secondly to provide current to the ignition and coil and thirdly to provide current to the vehicle's auxiliaries whilst the generator is not working. One other function is to act as a voltage load leveller as part of the vehicle's electrical circuits whilst the generator is operating.
The conventional SLI battery system is an advanced version of the original Plante reversible cell. During it's development, the basic principles utilized by Plante have still been retained up to the present time. That is, the battery consists of a series of cells having two opposing electrodes. The cells produce 2.2 volts generally. This configuration has proved to be suitable as a starter battery.
When batteries were first adapted for the supply of starting current, the automobile was quite different to what it is at present. Indeed, the motor vehicle has changed quite markedly in comparison to the battery. It is no longer as important to supply just cranking current for the vehicle. The modern vehicle is equipped with many electrical and electronic devices which present a major contrast in auxiliary current requirements for the battery.
Vehicle manufacturers, whilst incorporating the various extra auxiliaries into the vehicle, are merely responding to consumer demands. These extra auxiliaries place further demands on a battery system which is becoming more and more obsolete because it was always designed primarily as a starting battery. Indeed, the starting function is still the major function of the battery but it is now obvious that changes in automobile designs must also demand changes in battery design to keep pace with consumer demands for more auxiliary power.
Attempts to overcome these problems have been made by a number of people. Thus U.S. patent specification No. 406822 in the name Dey shows a battery which is divided into two cell groups by an internal dividing plate. U.S. Pat. No. 1924959 in the name of Patterson shows four cells two of which are in series and two of which can be between parallel or series combinations by the throwing of a switch. The cells are totally separate. U.S. Pat. No. 3029301 in the name of Strider shows a construction in which two battery parts are provided in series so that six and twelve volt voltage sources can be provided. U.S. Pat. No. 3242009 in the name of Schilke shows the construction in which two battery parts are provided but these are used to provide a number of different voltages. U.S. Pat. No. 3475221 in the name of Jordan shows two separate batteries in one container.
U.S. Pat. No. 3758345 in the name of Toth shows a construction in which a small auxiliary battery is provided in a shaped recess formed in the main plate. U.S. Pat. No. 3883368 in the name of Kordesch shows a construction in which two or more current rates are provided by the use of different types of electrode and, U.S. Pat. No. 4684580 in the name of Cramer shows a construction wherein the casing for the battery has a pocket or recess into which a second or auxiliary battery can be provided. None of these specifications show a construction wherein the problems of the large but short duration current required for cranking and the lower but longer duration demand required by the auxiliaries is able to be coped with in a single battery construction. U.S. Pat. No. 3883368 does indicate a battery which is able to cope with differing current rates but this is only achieved by the use of different types of electrodes. Such an approach is impractical as a SLI battery. U.S. Pat. No. 4684580 in the name of Cramer could provide a construction in which different current draw offs are provided but this is achieved only by the use of two quite separate and distinct batteries, one of which is able to be mounted on the other. Such double battery constructions require extensive changes to be made to the vehicle electrical architecture.
It is therefore an object of the present invention to provide a battery which will obviate or minimize the foregoing disadvantages or which will at least provide the public with a useful choice.